The lost continent that took 375 years to find

    It was 1642 and Abel Tasman was on a mission.

    The seasoned Dutch sailor, sporting a flamboyant mustache, a bushy goatee, and a penchant for heavy-handed justice (he tried to hang some of his crew by a drunken outburst) was confident of the existence of a vast continent in the southern hemisphere. .. and was determined to find it.

    At the time, that part of the world was still largely mysterious to Europeans, but they had an unshakable belief that there must be a large land mass there, preemptively named Terra Australis, to balance their own continent in the north.

    The fixation dates back to Ancient Roman times, but it was not until the 17th century that it was to be put to the test. And so, on August 14, 1642, Tasman set sail from his company’s base in Jakarta, Indonesia, with two ships. small and headed west, then south, then east, and finally ended up in the South Island of New Zealand.

    His first encounter with the local Maori did not go well: on the second day, several rowed in a canoe and rammed a small boat that passed messages between the Dutch boats. Four Europeans died.

    Later, the Europeans fired a cannon at 11 more canoes; It is not known what happened to his targets. And that was the end of his mission: Tasman named the fateful place Mo Ordeners Baij (Bay of Assassins), with little sense of irony, and sailed back home several weeks later without even have set foot in this new land.

    While he believed he had discovered the great southern continent, it was evidently not the commercial utopia he had envisioned. It did not return. (By then, Australia was already known, but Europeans thought that it was not the legendary continent they were looking for. Later, it received the name Terra Australis when they changed their minds.) Tasman did not know that all the time there was was right. A continent was missing.

    In 2017, a group of geologists made headlines when they announced the discovery of Zelandia (or Zealandia) – Te Riu-a-Māui in the Maori language – a vast continent of 4.9 million square kilometers, roughly six times the size of Madagascar. .

    Although the world’s encyclopedias, maps, and search engines had long insisted that there are only seven continents, the team confidently informed the world that that was wrong.

    In the end it turns out that there are eight. And the latest addition breaks all records, being the smallest, finest and youngest continent in the world.

    The problem is that 94% are underwater, with only a handful of islands, like New Zealand, emerging from their ocean depths. He had been hiding all this time. “This is an example of how something very obvious can take a while to discover,” says Andy Tulloch, a geologist at Crown Research Institute in New Zealand GNS Science, who was part of the team that discovered Zealand. .But this is only the beginning.

    Four years later, the continent is as enigmatic as ever, with closely guarded secrets under 2 km of water. How was it formed? What lived there? And how long has it been under water?

    A laborious discovery

    In fact, Zealand was always difficult to study. More than a century after Tasman discovered New Zealand in 1642, British cartographer James Cook was sent on a scientific journey to the southern hemisphere.

    His official instructions were to observe the passage of Venus between the Earth and the Sun, in order to calculate how far the Sun is.

    But he also carried a sealed envelope, which he was instructed to open when he had completed the first task. It contained a top-secret mission to discover the southern continent, where he possibly sailed directly before reaching New Zealand.The first real clues to the existence of Zealand were collected by Scottish naturalist Sir James Hector, who attended a trip to inspect a series of islands off the south coast of New Zealand in 1895.

    After studying its geology, he concluded that New Zealand is “the remnant of a mountain range that formed the crest of a large continental area that stretched south and east, and is now submerged.” , knowledge of a possible Zealand remained hidden, and very little happened until the 1960s.

    “Things happen quite slowly in this field,” Nick Mortimer, the GNS Science geologist who led the 2017 study, tells the BBC. In the 1960s, geologists finally agreed on a definition of what a continent is: broadly speaking. , is a geological area with high elevation, a wide variety of rocks, and thick crust.

    It also has to be big. “It can’t be a small piece,” says Mortimer. This gave the geologists something to work with: If they could collect the evidence, they could prove that the eighth continent was real.

    Still, the mission stalled: discovering a continent is complicated and expensive, and Mortimer notes that there was no urgency.

    Then, in 1995, American geophysicist Bruce Luyendyk again described the region as a continent and suggested naming it Zealand.

    From there, Tulloch describes his discovery as an exponential curve.

    Around the same time, the United Nations Convention on the Law of the Sea came into force, finally providing compelling motivation.

    It establishes that countries can extend their legal territories beyond their Exclusive Economic Zone, which reaches 370 km from their coasts, to claim their “extended continental shelf”, with all the mineral and oil wealth that this encompasses. If New Zealand could prove that you are part of a larger continent, you could increase your territory six times.

    Suddenly, there was a large amount of travel funds to survey the area and the evidence gradually accumulated. With each rock sample that was collected, Zealand’s case got better. The final flourish came from satellite data, which can be used to track small variations in Earth’s gravity in different parts of the crust to map the seafloor.

    With this technology, Zealand is clearly visible as a warped mass almost as large as Australia.

    When the continent finally made itself known to the world, it opened up one of the most important maritime territories in the world.

    “It’s great,” says Mortimer, “if you think about it, every continent on the planet has different countries, [but] there are only three territories in Zealand.” In addition to New Zealand, the continent encompasses the island of New Caledonia, a French colony. famous for its dazzling lagoons, and the tiny Australian territories of Lord Howe Island and Ball’s Pyramid.

    The latter was described by an 18th century explorer as “no bigger than a ship.”

    A mystery

    Zealand was originally part of the ancient supercontinent of Gondwana, which formed about 550 million years ago and essentially grouped all of the land in the southern hemisphere.

    It occupied a corner on the east side, where it bordered others, including half of western Antarctica and all of eastern Australia. Then, about 105 million years ago, “due to a process that we do not yet fully understand, Zealand began to move away, ”says Tulloch. Continental crust is typically about 40 km deep, significantly thicker than oceanic crust, which is typically about 10 km.

    As it tightened, Zealandia ended up stretching so much that its crust now only extends 20 km downward.

    Over time, the continent, as thin as a wave, sank, though not to the level of normal oceanic crust, and disappeared under the sea. Despite being fine and submerged, geologists know that Zealand is a continent due to to the type of rocks found there.

    The continental crust tends to be made up of igneous, metamorphic, and sedimentary rocks, such as granite, shale, and limestone, while the ocean floor is typically made up of igneous rocks like basalt.

    But there are still many unknowns.

    The unusual origins of the eighth continent make it particularly intriguing and quite puzzling to geologists.

    For example, it is still unclear how Zealand managed to stick together when it is so thin; How it doesn’t disintegrate into tiny microcontinents Another mystery is exactly when Zealand ended underwater, and if it ever actually consisted of land.

    The parts that are currently above sea level are ridges that formed when the Australian and Pacific tectonic plates wrinkled together.

    Tulloch says opinion is divided as to whether it was always submerged apart from a few small islands, or whether it was once completely dry land. This also raises the question of who or what lived there. With its mild climate and range of 101 million square kilometers, Gondwana was home to a wide variety of flora and fauna, including the first four-limbed land animals and, later, an abundance of the largest ever to inhabit the Earth: titanosaurs.

    So could the rocks of Zealand be filled with their preserved remains?

    A debate about dinosaurs

    Fossilized land animals are rare in the southern hemisphere, but the remains of several were found in New Zealand in the 1990s, including the rib bone of a giant long-tailed, long-necked dinosaur (a sauropod), a dinosaur a beaked herbivore (a hypsilophodon) and an armored dinosaur (an ankylosaur).

    Then, in 2006, the foot bone of a large carnivore, possibly a species of allosaurus, was discovered on the Chatham Islands, about 800 km east of the South Island.

    Fundamentally, all the fossils date from after the continent of Zealand separated from Gondwana.

    However, this does not necessarily mean that there were dinosaurs roaming most of Zealand; these islands may have been sanctuaries while the rest drowned, as it is now.

    “There is a long debate about this, about whether it is possible to have land animals without continuous land, and if without it, they would have become extinct,” says Sutherland. The plot thickens with one of New Zealand’s strangest and most beloved inhabitants, the kiwi, a plump, flightless bird with whiskers and feathers that resemble hairs.

    Interestingly, its closest relative is not believed to be the Moa – which is part of the same group, the ratites, and which lived on the same island until its extinction 500 years ago – but the giant elephant bird, which stalked the forests of Madagascar. until just 800 years ago, the finding has led scientists to believe that both birds evolved from a common ancestor that lived in Gondwana.

    It took 130 million years to completely break apart, but when it did, it left fragments that have since spread around the world, forming South America, Africa, Madagascar, Antarctica, Australia, the Arabian Peninsula, the Indian subcontinent and Zealand. .

    This, in turn, suggests that at least part of the now-submerged Zealand remained above sea level the entire time.

    About 25 million years ago, the entire continent, possibly even the entirety of New Zealand, is believed to have sunk under water.

    “It was thought that all the plants and animals must have colonized later,” Sutherland says. So what happened?

    Although it is not possible to collect fossils from the seafloor of Zealand directly, scientists have been probing its depths by drilling.

    “Actually, the most useful and distinctive fossils are those that form in very shallow seas because they leave a record,” Sutherland says. “There are trillions and trillions of tiny fossils that are very distinctive.” In 2017, a team carried out the most extensive studies of the region to date and drilled more than 1,250 meters into the seafloor at six different sites.

    The cores they collected contained pollen from land plants, as well as spores and shells from organisms that lived in warm, shallow seas. “If you have water 10 meters deep or something like that, then there’s a good chance there is land around as well.” says Sutherland, who explains that pollen and spores also point to the possibility that Zealand was not as submerged as previously thought.

    A twist (literal)

    Another lingering mystery can be found in the shape of Zealand. “If you look at a geological map of New Zealand, there are two things that really stand out,” says Sutherland.

    One of them is the Alpine Fault, a plate boundary that runs the length of the South Island and can be seen from space.

    The second is that New Zealand’s geology, as well as that of the continent in general, is strangely skewed.

    Both are divided in two by a horizontal line, which is where the Australian and Pacific tectonic plates meet.

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